Heat-sealable gusseted bag



V. J. WEMLINGER HEAT-SEALABLE GUSSETED BAG 7 Sept. 22, 1970 Filed Oct.18, 1968 Elli 52.: it

A 3 m F.

FIG.

INVENTOR VINCENT J. WEMLINGER BY M ATTORNEY United States Patent3,529,765 HEAT-SEALABLE GUSSETED BAG Vincent J. Wemlinger, Wilmington,Del., assignor to E. I. du Pont de Nemours and Company, Wilmington,Del., a corporation of Delaware Filed Oct. 18, 1968, Ser. No. 768,712Int. Cl. B65d 33/22 U.S. Cl. 229-62 5 Claims ABSTRACT OF THE DISCLOSUREAn improved gusseted, step-down, heat-sealable, laminated bag which hasan improved heat-seal can be produced by altering the construction of anormal heatsealable step-down bag by continuing the step-down to one plythrough the gusseted portion of the bag to eliminate the excessivethickness of the gusseted area and improve the heat-seal at the innerend of the gusset.

In the packaging of hygroscopic materials the largest problem to beovercome is that during shipment and storage the material tends to pickup excessive amounts of water. The best method to prevent the materialfrom picking up moisture is to ship it in sealed cans, but this is alsothe most expensive packaging method. A less expensive means of shippingsuch materials is paper bags. The major drawback of paper bags is thatthey are extremely permeable to water. Thus, it is necessary to coat orline the bags with some form of Water-impermeable material such as aplastic coating or bag. Adding a separate plastic coating to the bag orinserting a plastic liner in a bag requires additional packaging stepswith the resultant increased cost in packaging. It is desirable thenthat the water impermeable protective layer be integrally constructedwith the bag itself.

Heat-sealable, multi-walled bags having a plastic foil and paperlaminated inner ply have been produced in a tubular bag which has nogussets. The main disadvantage of this type of bag is that when filledthe corners of the bag protrude out beyond the sides of the bag and aresubject to abuse and tearing, which may result in damage to theheat-seal. Gusseted multi-wall heat-scalable bags have two distinctproblems: first, they are ditficult to seal due to the number ofthicknesses (plies) of paper at each end where the gusset is formed(i.e., on a four-ply bag the gusseted area would be 16 plies thick whilethe center portion of the top of the bag would be only 8 plies thick).This results in great difiiculty in heat-sealing through 16 plies at oneportion of the bag and only 8 plies at another portion of the bag;second, the step-down from the gusseted part of the bag to the centerpart of the bag (from 16 plies to 8 plies) results in a small pinholearea in which it is very ditficult to effect a complete seal. Thisallows moisture to enter the bag and on storage or shipment, themoisture content of the product becomes too high.

Applicant has discovered that by cutting out the outer plies from thegusseted area where the heat seal is to be made (the three outer pliesin a four-ply bag) and removal of the three outer plies across the faceof the bag at the end to be sealed, would result in a maximum thicknessin the gusseted area, on a four-ply bag, of seven plies in the gussetedarea and 5 plies in the non-gusseted area across the face at the end ofthe bag. This minor difference in the number of plies allows a betterand more complete heat-seal to be eifected at lower temperatures with noreduction of bag strength.

FIG. 1 shows a front view of the open bag of FIG. 4.

FIG. 2 shows a side view of the open gusseted bag of FIG. 4.

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FIG. 3 shows a top view and FIG. 3A shows one end blown up of thegusseted bag of FIG. 4.

b FIG. 4 shows a perspective view of the open gusseted Referring to thedrawings, the heat-sealable gusseted bag 11 of this invention can bemade on conventional gusseted bag-making machinery. In the process ofmaking gusseted bags, it is common in the art to make a stepdown cutarrangement at the bag ends to provide a closure device. As shown inFIG. 1, the step-down cut arrangement is made by cutting the bag at line4 to remove several plies of material, making a second cut at line 2 toremove several more plies of material, and cutting the bag to length atline 12. This results in a flap 6 which is thinner between lines 2 and12 than between lines 2 and 4 and which is thinner than face 10 of thebag. The bag is then folded along line 4 which forms ilap 6 which can bestapled, sewn or sealed with adhesives.

The heat-scalable bag of this invention is formed much like theconventional gusseted bag in that the out along line 4 removes allmaterial but the inner ply 5 from face 10 in the area between lines 2and 4 and the cut along line 2 leaves only the outer plies of face 9. Inaddition, in the gusseted area, there is another cut made between lines2 and 4 along line 3 to remove the outer plies 1 and leave the inner ply5 in the gusseted area on both sides of the bag.

The heat seal is then formed in the area between lines 2 and 3(extended). The bag is then folded along line 4 and sealed, whichresults in an end flap 6 similar to flap 8. Due to the small number ofplies difference between the gusseted areas and the center of the sealarea where the seal is made, a continuous uninterrupted seal can beeffected. The seal area is also made non-load bearing by making the foldof the bag flap along line 4 which puts the seal area back in the flaprather than at the end of the bag. This novel step-down cut arrangementcan be used to form an airtight seal at both ends of the bag.

The face width A and finished bag length B can be of any desired widthor length. The gusset width C can be of any desired width. The gussetwidth C will determine the depth of gusset line 7.

Lines 3 and 4 can be located at any desired distance from line 2 so asto remove sufficient material to allow a proper sealing of theheat-sealable material. The minimum distance that lines 3 and 4 can befrom line 2 is approximately A3" while the maximum distance is determined by economics and strength requirements of the end flap. It isnot necessary that lines 3 and 4 be at different heights. Lines 3 and 4can be a continuous line.

As described above, the bag must be of multi-wall construction to beable to effect the novel step-down feature in the gusseted area of thebag of this invention. The inner ply must be heat-scalable and from 1 to10 mils in thickness. It can be composed of any heat-scalablethermoplastic resin or any laminate of heat-sealable material plus otherbarrier material. The preferred laminate structure of the inner ply is akraft paper of approximately 40 pound weight on the outside, at least /2mil of polyethylene, preferably .5 to 3 mils of polyethylene, at least 3mil aluminum foil, preferably .35 to /2 mil aluminum foil, and at least/2 mil of a copolymer comprising 89% by weight of ethylene, 11% byWeight of methacrylic acid which is about 60% neutralized with zinc orsodium ions, 500 ppm. of Santowhite powder and has a melt index of 1,preferably .5 to 3 mils of said copolymer.

The outer plies can be of any number depending on the strengthrequirements of the bag. Any type of normal bagging paper or materialcan be used to form the outer plies. Among the types of material thatcan be used to form the various plies of this bag are kraft paper,extensible crepe paper, burlap, and asphalt laminates.

The bags of this invention can be made on continuous conventonal bagproduction machinery and can be supplied by a bag manufacturer with oneend closed and sealed or can be supplied with both ends open. Anadhesive is normally used to close the end flaps after heat sealing butany other conventional closing method that doesnt rupture the bags sealcan be used.

EXAMPLES 1-9 50 lb. bags incorporating the novel step-down feature ofthis invention and used in these examples are constructed of 4 plies asfollows: (1) an inner laminated ply consisting of one 3 milthermoplastic resin layer (said resin being a copolymer comprising 89%by Weight of ethylene, 11% by weight of methacrylic acid which is about60% neutralized with zinc or sodium ions, 500 ppm. of Santowhite powderand has a melt index of 1), one .5 mil aluminum foil layer, one 2 milpolyethylene layer and one 40 lb. kraft paper layer, respectively frominside to outside; (2) one layer of 50 lb. kraft paper; and (3) twolayers of 60 lb. kraft paper as the outer two layers.

The bags were filled with a copolymer comprising 89% by weight ofethylene, 11% by weight of methacrylic acid which is about 60%neutralized with zinc or sodium ions,

I claim:

1. A multiwall gusseted bag comprised of two multiply opposing facesintegrally connected by multi-pl gussets and having a heat-sealedclosure at one end and at least one end a stepped-down closurecomprising a moisture impervious inner heat-scalable ply having auniformly cut end and at least one step cut outer ply such that at saidend having the stepped-down closure, said outer ply covers and extendsabove said heat-sealable ply On one face of said bag and extends alongsaid heat-scalable ply on said other face and said gusseted areas towithin a minimum distance of about /8 inch from said uniformly cut endof said heat-sealable ply to form said stepped-down closure device.

2. The bag of claim 1 in which the heat-sealable inner ply is from about1 to about 10 mils in thickness.

3. The bag of claim 2 in which the heat-sealable inner ply is formed ofa thermoplastic resin material.

4. The bag of claim 2 in which the heat-sealable inner ply is a laminatestructure.

5. In a heat-sealable multiwall gusseted bag having multi-ply gussetsand two multi-ply stepped-down faces at at least one end to form aheat-sealable closure device, the improvement which comprises continuingthe stepdown cut which exposes at least about A; inch of the innerheat-scalable ply and extends across one face of said bag through thegusseted area to expose at least about inch of the inner heat-scalableply, to reduce thickness in the gusseted area and facilitate heatsealing of the bag.

TABLE I Average Average original final moisture moisture content content(p.p. m.) Date ppm.) Ex. No. Shipped to Shipped l'rom- Date in containertested in container Secaucus, N.I. Orange, Tex 1 /2 /67 175 2/23/68 326do ..d 175 2/23/68 357 175 2/23/68 281 175 3/9/68 238 175 3/9/68 485 1753/9/68 386 175 5/14/68 318 175 14/68 610 175 5/14/68 336 175 5/14/68 2,930

500 ppm. of Santowhite powder and has a melt index References Cited of1.

The moisture content of the resin going into the bags UNITED STATESPATENTS is measured and controlled as the resin is placed in the2,975,955 3 19 1 Mccurry 229 bags and the bags are heat sealed and gluedshut with adhegiva The bags were then shipped and stored and tested for1,062,748 3/1967 Great Britain moisture content several months later.Data 1s shown in Table I. Bag 8 was damaged on one corner in shipment 55or storage.

EXAMPLE 10 DAVID M. BOCKENEK, Primary Examiner US. Cl. X.R.

WW5) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,5gg65 Dated September 22, 1910 Inventor) Vincent J. Wemlinger It iscertified that error appears in the above-identified patent and thatsaid Letters Patnt are hereby corrected as shown below:

Column l, Claim 1, lines 3- 4, the word "at" is missing (at at least).

SIGNED AN?) .EALEP "91241970 mwudmnadnl mm #1:: A Officer l'onmissiozmor

